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May 2, 2007

Christmas Tree Scouting Report #6 - May 2, 2007

Weekly newsletter compiled by Sandy Gardosik, PA Department of Agriculture.

Canaan Fir is beginning to break bud in Adams County this week. When new growth was examined on trees exhibiting damage from balsam twig aphid, "stem mothers" and newly laid nymphs were found between the needles and under the bud scale.

In Northumberland County the buds were still tight on the true firs and the "stem mothers" were found feeding on the old needles. The "stem mothers" overwinter in the egg stage and begin hatching in early spring. When the new growth on true firs are close to breaking the "stem mothers" are mature and will begin laying live young which will feed on the new growth and cause the twisting and stunting of the new needles. Spraying near bud swell will insure all overwintering eggs are hatched and will prevent damage to new growth.

Spruce spider mites began to hatch last week in Berks, Dauphin and Lancaster counties on Balsam, Canaan and Fraser fir. This week egg hatch was observed in Northumberland County on Fraser fir. Growers in the northern counties of Pennsylvania should be scouting for SSM hatch. Using a 10-20x hand-lens examine twigs showing symptoms of mite feeding for eggs and newly hatched larvae. Another option is taping branches over a white surface waiting a few second then look for tiny dark moving dust specks that smear red. If mites are present spray with a registered insecticide and follow with a second spray 7-10 days apart unless stated otherwise on the label.

The Douglas fir needle midge is beginning to emerge from it's overwintering site beneath Douglas fir in Bucks and York counties. The adult fly is only about 1/8 inch long, orange and fragile looking. Eggs were found under bud scales and between needles and usually appear within 2-3 days after adults emerge. Control is directed to the adult flies. In Bucks County bud break was less then 10% so waiting till you apply your first application for Rhabdocline needle cast in theory would be to late. Bud break was closer to 10% bud break in York County but eggs were already present.  Monitoring for spring emergence with the cardboard box traps (refer to Scouting Report #4) will give you an idea at your farm how early the midge emerges in comparison to your first application for Rhabdocline needle cast. Orthene TT&O Spray 97 is registered for the control of the DFNM and states" application should be made no more than 2 weeks prior to bud burst". Indicating that spraying before the midge emerges my give best control.

Douglas fir bud break was near 10% in southern Adams and York counties this week. Growers should consider planning for their first application for rhabdocline needle cast when 10% of their trees begin to break bud.

Eggs of the Cooley spruce gall adelgids on Douglas fir and Colorado blue spruce can be found underneath the cottony white waxy threads in Bucks, Cumberland, Dauphin, Northumberland, Schuylkill, and York counties. This is an indication that the spray period has come to an end. Now that the buds are beginning to break eggs will hatch and nymphs will be in the new growth of Douglas fir. Feeding by the Cooley spruce gall nymphs causes needle kinking on Douglas fir. On Colorado blue spruce feeding by the nymphs causes gall formation. On Norways it is the eastern spruce gall adelgids that cause gall formation and eggs were found in York County. Eggs are pink in color on Douglas fir and yellow on Blue spruce and Norway spruce.

Eggs of the pine needle scale were found on white pine in Adams, Lebanon and Scotch pine in Jefferson and York counties. PNS over winter as tiny red eggs beneath the dead female's scale cover. This scale has two generations per year in Pennsylvania. Look for tiny red crawlers beginning mid-May and again in mid-July.

Weevil active was observed on white pine in Northumberland County this week. Eggs were found in the terminal leader of white pine when feeding damage was observed in York County.  Most growers have applied their sprays to control this weevil for the season. The only method for control will be pruning out damage if signs of infestation is noticed in the field later in the season.